The fate of Amelia Earhart is an unsolved mystery that has fascinated aviation watchers for decades.

Earhart, who had already become the first woman pilot to fly solo over the Atlantic Ocean, attempted to fly around the world with second navigator Fred Noonan in 1937. The pair and the Lockheed Model 10 Electra they were flying went missing over the Pacific Ocean near Howland Island. Neither their bodies nor the aircraft were recovered, despite an extensive and costly search.

While many experts believe the Electra ran out of fuel and crashed into the sea, others speculated the pair made a crash landing on nearby Gardner Island and died there.
But other wild theories about Earhart's fate in particular continue to swirl: She was a U.S. spy, she was captured and killed by the Japanese, she survived and moved to New Jersey under an assumed name, she and Noonan eloped to escape her fame, and she was even abducted by aliens.

Oakland Tribune via AP

2. FLIGHT 19 (1945)

On December 5, 1945, five Navy torpedo bombers took off from Florida on a training mission known as Flight 19. The five planes and the 14 crew members they held disappeared and were never fully recovered. A rescue plane sent to search for the Flight 19 members also went missing with its 13-man crew, assumed to have exploded in the air.

Flight 19 became one of the earliest tragedies linked to reports of supernatural events and plane disappearances in the "Bermuda Triangle" region.

According to a Navy report, instructor Lieutenant Charles Taylor became hopelessly lost when his compasses stopped working, and he told the other Flight 19 members to ditch their aircraft when fuel dipped below a certain level.

The Navy initially blamed the Flight 19 loss on pilot error, but Taylor's mother protested that conclusion given that no bodies or wreckage were found. After much debate, the Navy eventually said Flight 19 was lost due to "causes or reasons unknown."

Scientific Search Project via AP

3. BSAA AVRO LANCASTRIAN STAR DUST (1947)

This British South American Airways flight vanished in the Andes during a snowstorm on August 2, 1947. There was no sign of the aircraft, which was traveling to Chile from Buenos Aires, or its 11 passengers for more than 50 years.
Finally, in January 2000, climbers found part of the wreckage and the occupants' remains on Mount Tupungato on the Argentina-Chile border. Argentinian officials examined the crash site and concluded that severe weather was to blame — and not the pilot, who had been accused of negligence in earlier reports.

That revelation, half a century later, explained why the plane likely crashed. But it didn't solve one of the oddest parts of the mystery: Star Dust's final Morse code transmission, "STENDEC," which the aircraft sent twice.
The STENDEC transmissions have been a source of intrigue for people who puzzle over the strange word, wondering whether it could be an anagram, some type of code, an acronym or something else altogether.

This U.S. military-chartered flight was transporting mostly American troops to Vietnam when it vanished shortly after refueling in Guam on March 16, 1962. All 107 people on board were presumed dead.
Despite a massive eight-day sea and air search in the Pacific, the plane was never found. The U.S. Civil Aeronautics Board said the flight probably exploded in midair, but speculation of sabotage ran rampant.

The image above shows the Lockheed Super Constellation in 1950, a similar plane to Flight 739.

Lockheed Corp via AP

5. USAIR FLIGHT 427 (1994)

USAir Flight 427 was minutes away from the end of its trip from Chicago to Pittsburgh on September 8, 1994, when the plane hit turbulence and corkscrewed to the ground at nearly 300 miles per hour. The aircraft shattered upon impact a mere 28 seconds after the turbulence began. All 132 people aboard died.

It took more than four years for officials to issue a report, which concluded that a problem with the Boeing 737-3B7's rudder valve was to blame for the tragedy.

Gene J. Puskar / AP

6. TWA FLIGHT 800 (1996)

All 230 people aboard TWA Flight 800 died when the Paris-bound plane exploded in midair shortly after it took off from New York City on July 17, 1996. Several witnesses reported seeing a "streak of light" and a fireball, leading to early theories that Flight 800 was downed by a missile, a bomb or even a meteor.

After a four-year investigation, the National Transportation Safety Board ruled that the TWA 800 explosion was caused by an electrical short circuit that ignited the plane's fuel tank. But conspiracy theories of a government cover-up have persisted ever since.

The missing Malaysia Airlines jet immediately drew comparisons to another aircraft that recently disappeared over open water: Air France Flight 447, which plunged into the Mid-Atlantic on June 1, 2009, with 228 people on board.
Some debris from the plane surfaced in the ocean the next day, but it took almost two years for authorities to recover the craft's "black box" recorder and assess what happened.
French officials released a final report in July 2012, more than three years after the crash. They concluded that both technical and human error caused the incident. The plane's automatic pilot system disengaged after the craft's external speed censors iced over. The pilots, left without essential information, inadvertently put the plane into a stall and it fell quickly into the sea.